t / t4018 / golang-complex-functionon commit unpack_trees: fix breakage when o->src_index != o->dst_index (7db1183)
   1type Test struct {
   2        a Type
   3}
   4
   5func (t *Test) RIGHT(a Type) (Type, error) {
   6        t.a = a
   7        return ChangeMe, nil
   8}